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Updated: Jun 7, 2026

Photo-Induced Cross-Linking of Unmodified Proteins (PICUP) Applied to Amyloidogenic Peptides
Published on: January 12, 2009
Photoinduced electron transfer from tryptophan to Ru(II)TAP complexes: the primary process for photo-cross-linking
Mateusz Rebarz1, Jonathan Ghesquière, Arnaud Boisdenghien
1Chimie Organique et Photochimie, Université libre de Bruxelles, CP 160/08, 50 Avenue Franklin Roosevelt, B-1050 Bruxelles, Belgium.
Abstract:
The photoreaction mechanism of [Ru(TAP)(2)(phen)](2+) and [Ru(TAP)(3)](2+) (TAP = 1,4,5,8-tetraazaphenanthrene) with tryptophan (Trp), N-acetyl-Trp, and Lys-Trp-Lys is examined. The existence of a photoelectron-transfer process from the amino acid unit is demonstrated by laser flash photolysis experiments. The back electron transfer (BET) from the reduced complex to the oxidized amino acid, occurring at the microsecond time scale, corresponds approximately to an equimolecular-bimolecular process; however, it is disturbed by another reaction, originating from the oxidized Trp. Moreover, in competition with the BET, the reduced and oxidized intermediates give rise to an adduct. The latter is clearly detected by gel electrophoresis experiments in denaturing conditions, with a system composed of an oligonucleotide derivatized at the 3' end by the Ru(II)TAP complex and hybridized with the complementary sequence functionalized at the 5' end by the tripeptide Lys-Trp-Lys. Thus, upon illumination, a cross-linking between the two strands is observed, which originates from the presence of a Trp residue.
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